This application claims the benefit of Korean Patent Application No. 2000-9857, filed on Feb. 28, 2000, which is hereby incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a digital television, and more particularly, to an apparatus for converting screen aspect ratio that converts the input images that are in a random screen aspect ratio into the images that are in different screen aspect ratio.
2. Discussion of the Related Art
Presently, there are many television broadcast standards in existence. In the United States, the most common standard is the National Television Systems Committee (NTSC) standard which provides for an interlaced image with a 4:3 aspect ratio having 525 lines per frame. The video data transmitted by the NTSC television broadcast signal is an analog signal that may be digitally sampled to yield 720 square pixels horizontally on each of 480 lines.
The horizontal and vertical resolution of an image is typically expressed as an array of pixels, for example an NTSC image is represented as 720xc3x97480. Generally, the 4:3 aspect ratio standards is called Standard Definition Television (SDTV).
Digital television (DTV) receivers are being implemented substantially in accordance with the transmission standards established by the Advanced Television Standards Committee (ATSC). A similar standard is the European Digital Video Broadcasting (DVB) standard. A compressed digital video system is described in the ATSC digital television standard document A/53, incorporated herein by reference.
The new DTV standards allow broadcasters to deliver virtually any format up to 1920xc3x971080 pixels. As such, DTV receivers must be capable of receiving and processing a multiplicity of video formats. Therefore, a need exists in the art for a television receiver that is capable of receiving a multiplicity of formats and automatically adjusting video and other processing parameters depending upon the format of a particular received signal. Specifically, a need exists for a video processing system suitable for use in such a multiple format television receiver.
Typically, television display systems are only capable of receiving one broadcast format. In the past that has been acceptable to consumers because only one television broadcast format was available in each location and the television broadcast standard was well established and therefore very stable. With the arrival of wide-TV and HDTV, it is envisioned that not only more than one broadcast standard will be available to consumers in many locations, but that existing standards will gradually become obsolete.
Following the most recent availability of digital television sets, the 16:9 screen aspect ratio generally shown in movie theaters, is expected to become popular. Already, even before the availability of digital television, the television sets with wide screen (e.g., 16:9 screen aspect ratio) capability have been sold in the market. Such wide screen television system adopts the formula of showing the existing 4:3 screen aspect ratio for general broadcast program while showing 16:9 screen aspect ratio for certain programs.
To show the programs that are broadcast in 4:3 screen aspect ratio on the wide screen, the related art devices generally adopt either one of the formulae of establishing regions where no signals are present on left and right edges of the screen. Such devices also produce an enlarged screen by eliminating the signals representative of the top and bottom regions of the display screen because the relative importance of these signals is less in their natures. Sometimes, a formula wherein these two methods are compromised is also used.
However, by being unable to optimally utilize the given screen space or by discarding a substantial portion of the received signals, these methods have problems of failing to respond properly to the improved resolution of the screen that has an 16:9 aspect ratio and to the conversion of the other image sources such as movie films, etc. The underlying causes of these are in the limited image signal processing capacity of the existing analog television and the restriction stemming from attempting to realize the necessary functionality using relatively simple interpolation or decimation and filtering only. Therefore, there is a need for a television display system that is capable of converting and displaying, for example, broadcast and computer generated images from 4:3 to 16:9 aspect ratios.
Accordingly, the present invention is directed to a screen aspect ratio conversion apparatus that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
It is an object of the present invention to provide an apparatus for converting screen aspect ratio that composes or generates the image information of the regions for which no signal is given by utilizing the image information that is estimated from previous or subsequent frames.
Another objective of the present invention is providing an apparatus for converting screen aspect ratio that composes the image information of the regions for which no signal is given by utilizing the motion information that is obtained from the inputted image.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
In order to achieve the above object, there is provided a television receiver system for displaying video signals received in a first format (for example, 4:3 aspect ratio) to a second format (for example, 16:9 aspect ratio) and operable with at least one of encoded bit stream signal and sampled video signal. The receiver system comprises a decoder for decoding the bit stream signal and outputting a decoded video signal and a motion vector signal included in the bit stream signal; first and second frame buffers for storing at least one of the decoded video signal and the sampled video signal; a motion vector estimation unit for estimating block motion vectors by comparing a first frame with a second frame stored in the first and second frame buffers and outputs an estimated motion vector signal, wherein the first and second frames are displaced in time; a motion vector filter for filtering at least one of the motion vector signal from the decoder and the estimated motion vector signal from the motion vector estimation unit by providing at least one of spatial and temporal filtering and producing a filtered motion vector signal; a global motion information extraction unit for extracting the global motion information from the filtered motion vector signal and outputting a global motion information signal; and a composite image generator for generating data for image signal lacking regions in a frame in response to the global motion information signal, the filtered motion vector signal and data from first frame buffer.
According to one aspect of the present invention, the aspect ratio conversion apparatus used in a receiver system further comprises a scene change detector for detecting scene change and outputting a scene change detection signal to the composite image generator.
According to another aspect of the present invention, the filtered motion vector signal is produced with the spatial filtering by establishing an Nxc3x97N window, where N is an integer, on a vector matrix representative of the motion vector signal and taking two-dimensional vector median filtering. Alternatively, the filtered motion vector signal is produced with the temporal filtering by taking scalar median filtering out of motion vector signal that correspond to the identical locations on the M number of frames, where M is an integer and the frames are preferably sequential in time.
According to another aspect of the present invention, the composite image generator uses only the filtered motion vector signal to generate the data for image signal lacking regions if the global motion information signal contains invalid global motion information. If the global motion information signal contains valid global motion information, the composite image generator compares the filtered motion vector signal with the global motion information signal and uses only the filtered motion vector signal if the difference between the filtered motion vector signal and the global motion information signal exceeds a predetermined quantity.
If the global motion information signal contains valid global motion information, the composite image generator compares the filtered motion vector signal with the global motion information signal and uses only the global motion information signal if the difference between the filtered motion vector signal and the global motion information signal is less than a predetermined quantity.
According to another aspect of the present invention, the composite image generator uses only the filtered motion vector signal to generate the data for image signal lacking regions if the scene change detection signal is enabled. If the scene change detection signal is disabled, the composite image generator compares the filtered motion vector signal with the global motion information signal and uses only the filtered motion vector signal if the difference between the filtered motion vector signal and the global motion information signal exceeds a predetermined quantity.
If the scene change detection signal is disabled, the composite image generator compares the filtered motion vector signal with the global motion information signal and uses only the global motion information signal if the difference between the filtered motion vector signal and the global motion information signal is less than a predetermined quantity.
According to another aspect of the present invention, the composite image generator comprises a composite image size calculation unit for calculating the size of a composite image in response to the global motion information signal and a size of a previous composite image; a parallel shift unit for parallelly shifting the first frame received from the first frame buffer in response to a result of the composite image size calculation unit and outputting a shifted image signal; a third frame buffer for storing the shifted image signal and outputting a composite signal; and an image conversion unit for producing the data for image signal lacking regions in a form of a background image signal in response to the global motion information signal, the filtered motion vector signal, the scene change detection signal and the composite signal, wherein the third frame buffer stores the composite signal which comprises the background image signal overwritten by the shifted image signal.
According to another aspect of the present invention, the size of the composite image signal is determined by the image conversion unit in response to the global motion control signal and the filtered motion vector signal.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide a further explanation of the invention as claimed.